Due to limitations of time and frequency resources, improving resource utilization efficiency is a target which is always pursued in communication technology MIMO technology can simultaneously transmit a plurality of data streams on a same time-frequency resource block by exploiting space domain and thereby effectively boost system throughput.
Two-dimensional (2D) MIMO transmission has been studied and adopted in some wireless communication systems, such as the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE). As for the 2D-MIMO, traditional antenna arrays are arranged horizontally to form a beam in a horizontal plane. In order to explore potential gain from 3-dimensional (3D) wireless channels, the 3D MIMO has already been discussed in the area of wireless communications, for example, in a 3GPP meeting. For example, 3D MIMO channel modelling has been discussed.
To obtain a 3D MIMO channel, the planar (2D) antenna array is going to be used to obtain the vertical spatial gain. As antenna dimensions and channel dimensions increase, the amount of feedback about channel state information (CSI) also increases. However, resources for measuring the channels and feedback channel capacity for feeding back the CSI are limited, which means that a new feedback structure needs to be proposed, and a new codebook for 3D MIMO needs to be designed, in order to facilitate an effective feedback.
In the latest 3GPP technical report, a 3D MIMO precoder structure has already been determined. The 3D MIMO precoder is divided into a long-term feedback and a short-term feedback. The long-term feedback provides a group of beams, whereas the short-term feedback selects a beam or column from the group of beams of the long-term feedback, and performs a phase adjustment between different antenna polarizations.
Embodiments of the present disclosure provide a solution related to the short-term feedback.